A treatise on levelling, topography, and higher surveying (1876)
Gillespie, W. M. (William Mitchell), 1816-1868, Staley, Cady, b. 1840, ed · New York, D. Appleton and company · leaf 178
s framed into apyramid, as in Fig. 200, with a long mastprojecting above, fulfil the first and lastconditions. The mast may be made ver-tical by directing two theodolites to it, andadjusting it so that their telescopes followit up and down, their lines of sight beingat right angles to each other.… … Fig. 201. Fig. 202. Fig. 203.
Surveying
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